2022 ANDSS Chem Prelims P2

This document consists of 22 printed pages. Setter: Ms Sheena Cheong O ANDERSON SECONDARY SCHOOL Preliminary Examination 2022 Secondary Four Express CANDIDATE NAME: CLASS: / INDEX NUMBER: CHEMISTRY Paper 2 6092/02 18 Aug 2022 1 hour 45 minutes 0800 – 0945h Candidates answer in the Question Paper. No Additional Materials are required READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions in the spaces provided. Section B Answer all three questions, the last question is in the form of either/or. Answer all questions in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 22. The use of an approved scientific calculator is expected, where appropriate. Section A Section B Total ______________________________________________________________________________

PRELIM 4E CHEM 2022 6092/02 2 Section A Answer all questions in this section in the spaces provided. The total mark for this section is 50. A1 (a) The diagrams can be used to represent the structures of organic compounds that produce a smell. A H3C — CH2 — CH = CH2 B H3C — CH2 — CH2 — CH2 — CH2 | O — H C H3C — CH2 — CH2 — CH2 — CH2 — CH2 | O — H D H3C — CH2 — CH2 — C = O | O — H E H3C — CH2 — CH2 — CH — CH3 | O — H F H3C — CH = CH — CH3 Use the letters A, B, C, D, E and F to answer the questions. Each letter may be used once, more than once or not at all. (i) Which compounds are isomers? ……………………………………………………………………………….. [1] (ii) Suggest one pair of compounds that undergoes a reaction to form an ester. ……………………………………………………………………………….. [1] (iii) Which compounds can decolourise aqueous bromine? ……………………………………………………………………………….. [1]

PRELIM 4E CHEM 2022 6092/02 3 (iv) Which compound can react with magnesium to produce a gas that extinguished a lighted splint with a ‘pop’ sound? ……………………………………………………………………………….. [1] (b) Crude oil produces a range of substances that have many uses. Which statements about the different fractions of crude oil are true and which are false? Put a tick (✔) in one box in each row. true false Petroleum is separated by different density into different fractions. Alkanes used in diesel fuel have lower boiling points than those used in motor cars. The fraction used as feedstock for making plastics is extracted from higher up the fractionating column than the fraction used for kerosene (paraffin). Each fraction contains a mixture of hydrocarbons. [2] [Total: 6]

PRELIM 4E CHEM 2022 6092/02 4 A2 (a) Ethanol can be manufactured by the catalysed addition of steam to ethene. Ethene is obtained from crude oil. The reaction is reversible and can be represented with the following flow scheme. (i) Write a balanced chemical equation for the catalysed addition of steam to ethene. ………………………………………………………………………………. [1] (ii) Give a reason why the unreacted ethene is recycled. ………………………………………………………………………………. ………………………………………………………………………………. [1] (iii) It is important that oxygen does not enter the reaction chamber. Suggest a reason why. ………………………………………………………………………………. ………………………………………………………………………………. [1] IN ethene and steam phosphoric acid catalyst absorbed on silica pellets reaction chamber optimum conditions: 300oC, 60 – 70 atm OUT liquid ethanol and water unreacted ethene recycled to top of reaction chamber gases are cooled

PRELIM 4E CHEM 2022 6092/02 5 (b) Temperature will affect both the rate of reaction and yield of ethanol produced. The graph shows the yield of ethanol that is made under different conditions. (i) Using information from the graph, state the temperature and pressure that would give the highest yield of ethanol. ……………………………………………………………………………….. [1] (ii) Explain why the optimum conditions for the production of ethanol are different from your answers in (b)(i). ……………………………………………..………………………………… ……………………………………………..………………………………… ……………………………………………..………………………………… [2] [Total: 6] pressure/atm

PRELIM 4E CHEM 2022 6092/02 6 A3 In 2010, the Nobel Prize Physics was awarded for production of graphene from graphite. Graphene is an allotrope of carbon consisting of a single layer of atoms arranged in a two-dimensional hexagonal lattice structure. Fig. 3.1 shows the structure of gra phene and Fig. 3.2 shows the structure of graphite. Fig. 3.1 Fig.3.2 (a) Graphene can be prepared from graphite using sticky tape. Use ideas about bonding and structure in graphite to explain why it is possible to create graphene by this method. ……………………………………………..…………………………………..…... ……………………………………………..…………………………………..…... ……………………………………………..…………………………………..…... [2] (b) Some of the properties of graphene include having high electrical conductivity and strength. Explain how graphene can conduct electricity and have high strength. ……………………………………………..…………………………………..…... ……………………………………………..…………………………………..…... ……………………………………………..…………………………………..…... ……………………………………………..…………………………………..…... ……………………………………………..…………………………………..…... ……………………………………………..…………………………………..…... [4] carbon atoms

PRELIM 4E CHEM 2022 6092/02 7 (c) Graphene is transparent hence it is suitable to overlay a monitor screen and function as a touchscreen. Explain why graphene is transparent. ……………………………………………………………………………………… ……………………………………………………………………………………… [1] [Total: 7] A4 Table 4.1 shows results of different tests conducted to compare the properties of two dibasic acid, sulfuric acid and tartaric acid, of the same concentration. Table 4.1 test sulfuric acid tartaric acid Universal Indicator red orange volume of gas collected 10 s after reacting with magnesium 14 cm3 6 cm3 volume of sodium hydroxide required for complete neutralisation of 25.0 cm3 of acid 22.00 cm3 22.00 cm3 (a) (i) Explain the difference between a strong acid and a weak acid. ………………………………………………………………………………. ………………………………………………………………………………. [1] (ii) Use relevant tests and results in Table 4.1 to explain which acid is the weaker acid. ………………………………………………………………………………. ………………………………………………………………………………. ………………………………………………………………………………. ………………………………………………………………………………. ………………………………………………………………………………. ………………………………………………………………………………. [3]

PRELIM 4E CHEM 2022 6092/02 8 (b) The reaction of tartaric acid with aqueous sodium hydroxide can be represented by the equation below, where the tartrate anion is given the symbol T. H2T(aq) + 2NaOH(aq) → Na2T(aq) + 2H2O(l) Calculate the concentration of tartaric acid in mol/dm 3, if 0.100 mol/dm3 of sodium hydroxide is used. [3] [Total: 7] A5 Proteins are n